How to find all possible subset of a set?

Question

write a program and please explain the logic with example.

Answer 1

Program:

#include <stdio.h>
#include <math.h>

void printPowerSet(char *set, int set_size)
{
    /*set_size of power set of a set with set_size
      n is (2**n -1)*/
    unsigned int pow_set_size = pow(2, set_size);
    int counter, j;

    /*Run from counter 000..0 to 111..1*/
    for(counter = 0; counter < pow_set_size; counter++)
    {
      for(j = 0; j < set_size; j++)
       {
          /* Check if jth bit in the counter is set
             If set then pront jth element from set */
          if(counter & (1<<j))
            printf("%c", set[j]);
       }
       printf("\n");
    }
}

/*Driver program to test printPowerSet*/
int main()
{
    char set[] = {'a','b','c'};
    printPowerSet(set, 3);

    getchar();
    return 0;
}

Time Complexity: O(n2^n)

Comments

I did not understand logic of "if(counter & (1<<j))" little explanation would be helpful.